The purpose of this project is to provide independent consultation on statistical and epidemiological methodology in the design, interpretation, and evaluation of clinical trials of diagnosis, treatment, and prevention of cancer, and other studies requiring this kind of expertise. For some studies the Section provides full statistical support, including development of detailed study plans; assistance in the design of appropriate study forms; supervision of randomization (for trials); collection, processing, and editing of data; performance of interim analyses during the progress of the study; preparation of progress reports; final analysis of study data; and collaboration in the preparation of scientific papers. Among the current projects are: HIV Prevention Trials. Consultation on intervention trial design and analysis is being provided to the NIAID, NIMH, and CDC on various aspects of the prevention of HIV infection and AIDS. PSA Levels and Development of Prostate Cancer. In collaboration with the Cancer Prevention Studies Branch, we are assessing the relation of levels of prostate-specific antigen (PSA) and change in PSA over time to subsequent prostate cancer. In addition to total PSA, free PSA and the ratio of free/total are being investigated. The primary source of data is the Alpha-Tocopherol Beta-Carotene Lung Cancer Prevention Trial in Finland. PSA has been measured on all cases of prostate cancer and on matched controls. A variety of data analytic approaches are being explored. State Laws on Youth Access to Tobacco. In collaboration with the Public Health Applications Branch, we are evaluating the extensiveness of state laws on youth access to tobacco, by developing and applying a rating system using information from the NCI State Cancer Legislative Database. Analysis of USDA Feeding Studies. We are collaborating with the Cancer Prevention Studies Branch on the analysis of a series of USDA feeding studies of women 20-40 years of age. Research is underway to study the complex relationships between blood lipids, hormone levels, and plasma carotenoid levels by phase of the menstrual cycle. Polyp Prevention Trial. We are providing full statistical support for the design, conduct and analysis of a multicenter dietary intervention trial among 2,000 men and women with a previous adenomatous polyp of the colon or rectum. We have recently contributed to two papers on the design of the study and the nutritional intervention. We are currently analyzing the results of a sub-study on the measurement of cell proliferation in approximately 350 of the participants. Study of the Adoption and Use of the Primary Care Nutrition Guide. The Section has provided statistical consultation to the Public Health Applications Branch on the design, planning, and implementation of a physician practice study evaluating the NCI Primary Care Nutrition Guide and a training course (based on the Guide) among internal medicine and family medicine practices.